The present invention relates to a method for heat treating and a thermal treatment equipment applying the method. Particularly, the invention relates to the thermal treatment equipment heating a substrate or a formed matter on the substrate by heated gas and the method for heat-treating using the equipment.
In a manufacturing process of a semiconductor device, thermal treatments aiming at oxidation, diffusion, gettering, and recrystallization after ion injection with respect to a semiconductor or a semiconductor substrate are programmed. A typical example of the equipment performing these thermal treatments is a hot wall type annealing furnace of horizontal type or vertical type, which is used widely.
The annealing furnace of horizontal type or vertical type is batch type equipment treating many substrates in a lump. For example, the vertical annealing furnace mounts a substrate on a suscepter formed by quartz horizontally and in parallel, and performs putting in and out to a reaction pipe by an elevator driving up and down. At outer circumference portion of a bell-jar type reaction pipe, a heater is provided so as to heat a substrate by the heater. It takes comparatively long time for rising time reaching the predetermined heating temperature and falling time cooling to temperature possible to take out because of the construction thereof.
Incidentally, in MOS transistor used for an integrated circuit, very high process accuracy is required as elements become fine. Especially, it needs to diffuse impurity at the minimum for forming thin junction. However, process taking long time for rising temperature and falling temperature as the annealing furnace makes forming thin junction difficult.
Rapid thermal anneal (described RTA hereafter) method is developed as thermal treatment technique performing rapid heating and rapid cooling. An RTA equipment heats a substrate or a formed matter on the substrate rapidly using infrared ray lamp so as to perform thermal treatment in short time.
A thin film transistor (described TFT hereafter) is well known as another form of a transistor.
The TFT is paid attention as technique possible to form an integrated circuit directly on a glass substrate. The technique is advanced for application development for new electronic device such as a liquid crystal display device. Especially, the FET forming impurity domains such as a source domain and a drain domain on a polycrystal semiconductor film formed on the glass substrate needs thermal treatment for activating and easing of distortion. However, the glass substrate has demerits that distortion point thereof is only 600 to 700° C. and it is broken easily by thermal shock.
In the vertical or horizontal type annealing furnace of the related art, it becomes difficult to obtain uniformity of heating temperature when size of the substrate is large regardless of whether substrate forming the integrated circuit is semiconductor or insulation material such as glass or ceramic. In order to obtain uniformity of temperature in substrate surface and between substrates, it needs to make pitch of treated substrate mounting horizontally and in parallel wide because of characteristic of gas flowing in the reaction pipe as fluid. For example, when a side of the substrate exceeds 500 mm, pitch of the substrate is necessary to take more than 30 mm.
Therefore, as the treated substrate is large, the equipment is necessarily large size. Because many substrates are treated in a lump, weight of substrates themselves increases, and suscepter mounting the treated substrate needs strength. Because of that, the weight increases, and operation of the machine carrying in and out the treated substrate becomes slow. Further, the instrument influences not only to increase of floor area occupied by the thermal treatment equipment but also to building cost for a building having withstand load of the floor. Thus, large sized equipment forms a vicious circle.
On the other hand, the RTA method processes piece by piece as premise so that load of the equipment does not increase extremely. However, difference in absorptance of lamp of light used for heating unit generates because of characteristic of the treated substrate and the formed matter thereon. For example, when a pattern of metal wiring is formed on the glass substrate, a phenomenon that the metal wiring is heated earlier and the glass substrate is broken by local distortion generates. Because of that, complex control such as adjusting rising speed is required.
The invention is aimed at solution of the problem, that is, the object of the invention is to provide a method activating impurity element added to semiconductor by short time thermal treatment and performing gettering process, and a thermal treatment equipment possible to perform such the thermal treatment.